Process for making casein fibers for felting



Patented Oct. 17, 1950 UNITED "STATE PATENT OFFICE 1 PROCESS FOR MAKING CASEIN FIBERS FOR, FELTING No Drawing. Application January 23, 1948,

Serial No. 4,054

9 (Granted under the act of March 3, 1883, as

5 Claims.

This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed if patented in any country, may be manufactured and used by or for the Government of the United States of America throughout'the world for governmental purposes without the payment to us of any royaltythereon.

This invention relates to a process for making casein fibers for felting, for example, in admixture with fur fibers. It particularly relates to casein fibers containing metals producing insoluble basic salts, such as aluminum, beryllium, chromium, or magnesium.

An object of this invention is to improve the felting and other properties of such fibers by subjecting them to a chemical hardening treatment under tension prior to a drying operation, the fiber being restrained from linear shrinkage during the drying. at

A further object is to prevent felting together during the drying under tension by subjecting amended April 30, 1928; 370 O. G. 757) ing acetic acid), and the fiber makes several loops before being wound onto a bobbin while maintained under tension. It is noted that the stretch of about 260% is carried out between the conical godet wheels and the second set of ordinary godet wheels. It is also noted that this 260% stretch is the final stretch mentioned. The expression maintained under tension is employed in its conventional sense and signifies merely restraint from linear shrinkage, as indicated below. Where stretching is carried out the term stretching is used. The bobbin is placed in a 5% aqueous formaldehyde solution containing 30% sodium acetate and having a pH 6 and held at 25 C. for 4-16 hours. The temperature of the bath is then raised to 70 C. and the treatment continued for an additional 16 hours. The fiber is then washed and dried on the bobbin to a moisture the fiber to a change in pH prior to thedrying.

cedures of the following illustrative examples:

Example I A aqueous solution of, casein containing 0.56% N'aOI-l is heated at 55 C. to deaerate it, thencooled to 25 C. and extruded at the rate of5.4= ml. per minute through 0.003 diameter orifices in a 250 hole spinneretteinto a precipitating bath. The tow is drawn away at the speed of 6.25 meters per minute, 32% jet stretch. The precipitating bath is 6% acetic acid containing 20% sodium sulfate, and the bath travel is approximately 20 inches. The fiber tow is next treated by passing over cone goclet wheels in a series of tenloops. The lower godet wheel is bathed by a heated aqueous solution containing 5% formaldehyde, 10% aluminum sulfate and 10% sodium sulfate. The temperature of'this bath is maintained at about 60 C. and thefiber is stretched approximately 100% while passing from the inner to the outer loop on the conical godet wheels, and then given a further stretch of about 260% by driving the next set of godet wheels at a surface speed of. ,33 meters per minute. On this second set of'godet wheels the lower wheel dips into the pH 6-8 wash bath consisting of a aqueoussodium acetate solution(containcontent of not more than 5%. 'Thefiber does not felt together during the drying, and is removed from the bobbin, cut into staple fiber approximately inch long, carded and stored.

Example II The fiber is produced and treated as described in the foregoing example except that after being held for 4-46 hours in the formaldehyde-sodium acetate solution at 25 0., the fiber is washed free of salts and dried on the bobbin to a moisture content of about 4-2%. The bobbin is then immersed for about 15 minutes in acetic anhydride at C., the fiber washed to remove acetic anhydride and acetic acid, and dried on the bobbin to a moisture content of not more than 5% before being cut into staple fiber.

Similar results are obtained using instead of a pH 6-8 wash bath consisting of 30% aqueous sodium acetate, a 30% solution of sodium formate at pH 6-8.

Casein fiber made by stretching the tow from a spinnerette in an acid and salt coagulating bath and hardened under tension will have a considerable amount of stored tension if allowed to dry While restrained from linear shrinkage. If the fiber is dried under tension to a low moisture level, 5% or less, before cutting into staple fiber, this stored stress will remain latent until the fiber is wet, whereupon an immediate shrinkag will take place. 7

However, casein fiber made by the conventional processes described in the literature will felt together while being dried under tension, and carding machinery will be unable to separate the ing caseinfiberis subjected to apH 68 wash bath immediately before winding on a bobbin or processing on advancing reels, the fibers will not felt together when dried under tension, and the process becomes operable. Aluminum is the usual metal employed in fiber manufacture but casein fibers containing other metals producing insoluble basic salts, such as beryllium, chromium or magnesium, may also be used.

Because casein fibers are often dyed, a partial acetylation process may be used to supplement the formaldehyde hardening of casein fibers intended for felting. This will raise their resistance to boiling dye baths and cut down the dye uptake. We have found that acetylation in acetic anhydride using acetic acid as a catalyst results in a relaxation of our improved fiber,and that better results are obtained if the fiber dried to moisture content of not more than 5% and preferably 2-l% is acetylated with acetic anhydride as in Example II above, or in mixtures of organic solvents and acetic anhydride for a short period.

Treatment of the fiber with progressively higher temperature formaldehyde baths at pH 6, and while the fiber is under tension, is another effective way of raising the boil resistance and cutting down the dye uptake of the fiber. These formaldehyde treatments, as well as the treatment with acetic anhydride, result in the fiber showing a second shrinkage component, one which is activated by successive application of hot water.

One aspect of our process can be characterized as making improved casein fibers for felting in admixture with fur fibers by treating a casein fiber formed at a pH lower than 6, and having contained in the fiber a soluble metal salt, with a washing bath at a pH of 6 to 8, hardening the fiber tow under tension, stabilizing the casein fiber, without relaxation of such tension, and finally lowering the moisture content, preferably to 2-4%, and cutting the fiber into staple lengths. The fibers are then mixed with fur fibers and subjected to known felting processes.

Having thus described ourinvention, we claim:

1. A process of making casein fibers for felting, comprising spinning aqueous alkaline casein solution into an acidic coagulating bath to form a tow,the acidic constituent of the bath essentially consisting of acetic acid, stretching the fiber, subjecting the fiber under tension to hardening with aqueous formaldehyde and aluminum salt, further stretching the fiber, treating the prestretched hardened aluminum containing fiber under restraint from linear shrinkage in a solution essentially consisting of an aqueous solution of a salt of the group consisting of sodium acetate and formate while maintaining it at a pH of 6-8, treating the fiber under tension with aqueous formaldehyde at a pH of about 6, drying the fiber, while restraining it from linear shrinkage, to a moisture content of not more than 5 percent, and cutting the fiber into staple lengths.

2. A process of making casein fibers for felting comprising spinning aqueous alkaline casein solution into an aqueous acetic acid coagulating bath to form a tow; stretching the tow, and subjecting it under tension to a hardening treatment with aqueous formaldehyde and aluminum sulfate; increasing the stretch and subjecting the pre-stretched tow under restraint from linear shrinkage and substantially without further stretching to treatment with a solution essentially consisting of an aqueous solution of an agent of the group consisting of sodium acetate and sodium formate at a pH of 6-8; treating the fiber under tension with a solution of aqueous formaldehyde and sodium acetate at a pH of about 6 at a temperature of about 25 C. for about 4 to 16 hours; continuing the treatment at about 70 0.; washing, and drying the fiber under restraint from linear shrinkage to a moisture content of about 5% or less, and thereafter cutting the fiber into staple lengths.

3. A process of making casein fibers for felting comprising spinning aqueous alkaline casein solution into an aqueous acetic acid coagulating bath to form a tow; stretching the tow, and subjecting it under tension to a hardening treatment with aqueous formaldehyde and a salt of a metal forming insoluble basic salts from the group consisting of aluminum, beryllium, chromium, and magnesium; increasing the stretch and subjecting the pre-stretched tow while maintained under tension to treatment with a solution essentially consisting of an aqueous solution of an agent of the group consisting of sodium acetate and sodium formats at a pH of 6-8; treating the fiber under tension with a solution of aqueous formaldehyde and sodium acetate at a pH of about 6 at a temperature of about 25 C. for about 4 to 16 hours; continuing the treatment at about 70 C.; washing, and drying the fiber under restraint from linear shrinkage to a moisture content of about 5% or less.

4. A process of making casein fibers for felting in admixture with fur fibers, comprising: spinning an aqueous alkaline casein solution into an aqueous coagulating bath to form a fiber tow, the coagulating bath essentially consisting of dilute acetic acid containing sodium sulfate, stretching the fiber about hardening'the fiber under tension with aqueous formaldehyde and aluminum salt, giving the fiber a further stretch, winding the fiber on a reel under tension and washing the fiber on the reel with a bath essentially consisting of aqueous sodium acetate containing acetic acid at a pH of 6-8, winding the fiber onto a bobbin under tension, treating the aluminum containing fiber thereon while restrained from linear shrinkage with aqueous formaldehyde containing sodium acetate at a pH of about 6 for several hours at about 25 C. and then for several hours at about 70 C., washing the fiber and drying it on the bobbin under restraint from linear shrinkage to a moisture content of not more than 5%, removing the fiber from the bobbin and cutting it into staple lengths.

5. A process of making casein fibers for felting comprising: spinning aqueous alkaline casein solution into a precipitating bath essentially consisting of dilute aqueous acetic acid containing sodium sulfate; stretching the fiber about 100% while it is passed through a bath of aqueous formaldehyde, aluminum sulfate, and sodium sulfate; further stretching the fiber about 260% and thereafter washing it at pH 6-8 in a bath essentially consisting of aqueous sodium acetate containing acetic acid; winding the fiber on a bobbin while maintained under tension and placing it in a bath essentially consisting of aqueous formaldehyde and sodium acetate at pH 6 for several hours; and Washing and drying on the bobbin to a moisture content of not more than 5%, whereby the stored stress will remain latent until the fiber is wet, and cutting into staple fiber.

ROBERT F. PETERSON. RICHARD w. JACKSON.

(References on following page),

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 6 Name Date Meigs Aug. 20, 1940 Lawrence et a1 June 3, 1941 Wormell July 21, 1942 Ferretti Jan. 11, 1944 10 Jacokes et a1 Jan. 18, 1944 Traill et a1. Feb. 8, 1944 Atwood Feb. 29, 1944 Watson Apr. 23, 1946 Atwood Sept. 24, 1946 15 Number Number Name Date Cline Oct. 15, 1946 Atwood Oct. 7, 1947 FOREIGN PATENTS Country Date Great Britain Nov. 10, 1938 Great Britain Nov. 22, 1938 OTHER REFERENCES News Ed., Amer. Chem. 800., Nov. 25, 1941, pages 1239 through 1244.

Brown et al., I. and E. Chem. 36 No. 12 (Dec. 1944), pages 1171-1175. 

1. A PROCESS OF MAKING CASEIN FIBERS FOR FELTING, COMPRISING SPINNING AQUEOUS ALKALINE CASEIN SOLUTION INTO AN ACIDIC COAGULATING BATH TO FORM A TOW, THE ACIDIC CONSTITUENT OF THE BATH ESSENTIALLY CONSISTING OF ACETIC ACID, STRETCHING THE FIBER, SUBJECTING THE FIBER UNDER TENSION TO HARDENING WITH AQUEOUS FORMALDEHYDE AND ALUMINUM SALT, FURTHER STRETCHING THE FIBER, TREATING THE PRESTRETCHED HARDENED ALUMINUM CONTAINING FIBER UNDER RESTRAINT FROM LINEAR SHRINKAGE IN A SOLUTION ESSENTIALLY CONSISTING OF AN AQUEOUS SOLUTION OF A SALT OF THE GROUP CONSISTING OF SODIUM ACETATE AND FORMATE WHILE MAINTAINING IT AT A PH OF 6-8, TREATING THE FIBER UNDER TENSION WITH AQUEOUS FORMALDEHYDE AT A PH OF ABOUT 6, DRYING THE FIBER, WHILE RESTRAINING IT FROM LINEAR SHRINKAGE, TO A MOISTURE CONTENT OF NOT MORE THAN 5 PERCENT, AND CUTTING THE FIBER INTO STAPLE LENGTHS. 